Labour members have been warned that selecting anyone but Tessa Jowell as the party’s candidate in next year’s Mayoral election will see the Tories controlling City Hall for a third consecutive term.

Dame Tessa started the race to become Labour’s candidate as the clear favourite, however in recent days it’s been suggested that she’s in danger of losing the nomination to Ed Miliband ally Sadiq Khan after he was named favourite to emerge as the candidate by bookmakers Paddy Power.

Mr Khan’s campaign has also been buoyed by a poll suggesting he could beat likely Tory candidate Zac Goldsmith.

All previous polling has suggested that Khan would lose against Mr Goldsmith and that only former Olympics minister Jowell could win for Labour.

The party has only ever won the Mayoralty once when it allowed former independent Mayor Ken Livingstone back into the party to avoid defeat in the 2004 contest. Mr Livingstone lost his re-election bid in 2008 to Boris Johnson and failed to take back City Hall at the 2012 contest.

Winning in London next year will be vital if the party is to show it can still prosper despite its unexpected defeat in this May’s general election.

Streatham MP Chuka Umunna, a close ally of Dame Tessa’s, today told party members: “She is the only Labour contender who can beat any Tory and she has the policies for London that focus on opportunity and not narrow tribalism which turns so many off from politics.”

He added: “London needs a Labour Mayor who can deliver. She is the candidate with an inspiring vision of a better future and, from Sure Start to the Olympics, Londoners know Tessa can deliver, and Labour supporters know she’s a winner.

“I’m not just giving Tessa my vote, I’m excited to be campaigning with her and giving her every bit of my support. She can do great things if we get behind her and that’s exactly what I intend to do by playing a full role in her campaign.”